• Applied Biological Chemistry
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• v.36 no.1
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• pp.45-50
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• 1993

A psychrotrophic microorganism isolated from Alaska pollack (Theragra chalcoramma) produced soymilk-clotting enzyme(s) with relatively low proteolytic activity. The isolate No. 268 was tentatively identified as Pseudomonas sp. Soymilk-clotting activity of the crude enzyme solution was observed at temperatures ranging from 20 to $60^{\circ}C$ and the optimum temperature was $40^{\circ}C$. When the crude enzyme solution was preincubated for 30 minutes, the clotting activity was stable at temperatures up to $30^{\circ}C$ and 75% of the activity was retained at $40^{\circ}C$. The clotting activity was decreased as the pH of soymilk was increased from 5.8 to 7.3.

• Clean Technology
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• v.22 no.3
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• pp.175-180
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• 2016

Tyrosinases catalyze the hydroxylation of a monophenol (monophenolase activity) and the conversion of an o-diphenol to o-quinone (diphenolase activity), which are mainly involved in the modification of tyrosine residues into 3,4-dihydroxyphenyl-alanine (DOPA) and DOPA/DOPAquinone-derived intermolecular cross-linking. Previously, we obtained a slightly acidic and cold-active tyrosinase, tyrosinase-CNK, by our recombinant protein approach. The enzyme showed optimal activity at pH 6.0 and 20 ℃ with an abnormally high monophenolase/diphenolase activity ratio and still had approximately 50% activity compared with the highest activity even in ice water. Here, we investigated reaction stability of the recombinant tyrosinase-CNK as a psychrophilic enzyme. The enzyme showed remarkable thermal stability at 0 ℃ and the activity was well conserved in repeated freeze-thaw cycles. Although water-miscible organic solvent as reaction media caused the activity decrease of tyrosinase-CNK as expected, the enzyme activity was not additionally decreased with increased concentration in organic solvents such as ethanol and acetonitrile. Also, the enzyme showed high salt tolerance in chaotropic salts. It was remarkably considered that 2⁺ metal ions might inhibit the incorporation of Cu²⁺ into the active site. We expect that these results could be used to design tyrosinase-mediated enzymatic reaction at low temperature for the production of catechols through minimizing unwanted self-oxidation and enzyme inactivation.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2004.10a
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• pp.384-387
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• 2004

겨울철 토양에서 ${\beta}-Galactosidase$를 생산하는 균주를 분리하였으며 동정한 결과 그람 음성 간균이고 Pantoea spp. 로 확인되었다. Pantoea spp. 균주의 세포 추출물로부터 DEAE-Sephacel chromatography와 affinity chromatography를 이용하여 ${\beta}-Galactosidase$를 분리하였다. Pantoea spp. 의 ${\beta}-Galactosidase$의 반응 최적 온도는 $45^{\circ}C$이이고 최적 pH는 $5.5{\sim}7.5$이고 열안정성을 조사한 결과 $45^{\circ}C$이상의 온도에서 불활성 되는 것으로 나타났고 E. coli에서 분리된 효소보다 저온에서의 활력이 좋았지만 상업적인 효소인 Kluyveromyces lactis (Validase) 보다는 낮았다.

• Korean Journal of Microbiology
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• v.55 no.1
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• pp.17-24
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• 2019

Bacteria in the polar region are under strong light and ultraviolet radiation. In this study, we investigated the effects of light on the growth of a psychrophilic bacterium, Sphingomonas sp. PAMC 26621, isolated from an Arctic lichen Cetraria sp. The growth of the strain in the light was lower than that in the dark. Surprisingly, thiamine increased the growth of Sphingomonas sp. PAMC 26621 in M9 minimal medium under light conditions. Thiamine increased the growth of the strain in a concentration-dependent manner along with ascorbic acid. N-acetylcysteine had no effect on the growth of the strain in the light. Thiamine and ascorbic acid also increased the activities of glucose-6-phosphate dehydrogenase and superoxide dismutase. The results of this study indicate that thiamine provided by the lichen symbiosis system plays an important role in light-induced oxidative stress in this Arctic bacterium as an antioxidant. Our study provide insight into the biochemistry and physiology of Arctic bacteria under strong light and ultraviolet radiation.